The invention relates to a new process for the production of alkylbenzenes.
Processes for producing biodegradable detergents are important because non-biodegradable detergents remain undissolved in sewage. When non-biodegradable detergents are aerated, large quantities of foam result. The diluted detergents solution often enter subsurface waters, which ultimately feed into the underground water strata, which serve many cities as a source of water supply. Occasionally, these detergents turn up in tap water in sufficient quantities to cause the water to foam at the tap.
To meet the public's demand for pure water, the petrochemical industry has attempted to develop biodegradable detergents. Alkylaryl-based detergents are more readily degradable by sewage bacteria if the alkyl substituent on the phenyl nucleus is of a simple, straight chain configuration than if it is of a more complex, branched chain structure. For example, detergent compounds with an alkyl side chain, such as: EQU CH.sub.2 --(CH.sub.2).sub.y --CH.sub.3
are more likely to be bacterially digested than detergents of the same chemical composition but in which the isomeric alkyl radical is a more highly branched chain, such as: ##STR1##
These biodegradable detergents are generally manufactured either: (1) by using molecular sieves or urea adduction to isolate C.sub.9 to C.sub.18 n-paraffins from mixtures containing the paraffins and converting the n-paraffins to an olefin-acting compound, such as a monohalogenated paraffin or a mono-olefin; or (2) by cracking of saturated paraffin waxes to produce a linear olefin. These olefin-acting compounds are then used to alkylate a mono-cyclic aromatic, such as benzene, and the resultant alkylaromatic is sulfonated and neutralized to form the desired detergent.
Catalytic reforming is a well known process that involves raising the octane rating of a naphtha. The reactions that occur during reforming include: dehydrogenation of cyclohexanes, dehydroisomerization of alkylcyclopentanes, dehydrocyclization of acyclic hydrocarbons, dealkylation of alkylbenzenes, isomerization of paraffins, and hydrocracking of paraffins. While most reforming catalysts contain platinum on an alumina support, some people have proposed using large-pore zeolites as a support. These large-pore zeolites have pores large enough for hydrocarbons in the gasoline boiling range to pass through. Catalysts based on these zeolitic supports have been commercially unsuccessful.
It would be advantageous if longer hydrocarbons could be subjected to dehydrocyclization to form alkylbenzenes for use in detergents, enhanced oil recovery surfactants, and lube oil additives. The end use would determine the preferred feed. For instance, hydrocarbons containing 16 to 22 carbon atoms per molecule would be useful feeds for a process making detergent-type products, while hydrocarbons containing from 25 to 40 carbon atoms per molecule would be ideal feeds for a process making lube oil additives.